Datastores should expose Close()

[raulk]

We should consider embedding io.Closer inside Datastore and upgrading all implementations to forward the call to the underlying closing method, as well as to perform any necessary cleanup (channels, goroutines, etc.):

• badger: https://godoc.org/github.com/dgraph-io/badger#DB.Close
• leveldb: https://godoc.org/github.com/syndtr/goleveldb/leveldb#DB.Close

[Stebalien]

YES (although we shouldn't rely on it for correctness).

[kevina]

YES (although we shouldn't rely on it for correctness).

Can you be more specific?

[Stebalien]

We should be able to close datastores so:

1. We can do a clean shutdown.
2. We can open, use, and then close a datastore without shutting down.

However, we shouldn't rely on datastores being correctly closed on shutdown (i.e., we should be able to crash).

(nothing surprising, just not very well put)